F214: Respiration

Question 0

What are catabolic reactions?

Answer 0

When larger molecules are hydrolysed to produce smaller molecules.

Question 1

What are anabolic reactions?

Answer 1

biochemical reactions where large molecules are synthesised from smaller ones.

Question 2

What is glycolysis?

Answer 2

A metabolic pathway where each glucose molecule is broken down to two molecules of pyruvate.
It occurs in the cytoplasm of all living cells.

Question 3

What is hydrolysis?

Answer 3

The breaking down of large molecules to smaller molecules by the addition of water.

Question 4

What is the site if the link action, Krebs cycle and oxidative phosphorylation?

Answer 4

Mitochondria.

Question 5

What does the link reaction do?

Answer 5

Converts pyruvate to acetate.

NAD is reduced.

Question 6

What does the Krebs cycle do?

Answer 6

Oxidises acetate to carbon dioxide.
NAD and FAD are reduced.
ATP is made by substrate level phosphorylation.

Question 7

What is oxidative phosphorylation?

Answer 7

The formation of ATP by adding a phosphate group to ADP.

In the presence of oxygen which is the final electron acceptor.

Question 8

What is chemiosmosis?

Answer 8

The diffusion of hydrogen ions through a partially permeable membrane, which is coupled to the generation of ATP.

Question 9

What is anaerobic respiration?

Answer 9

The release of energy from subtrates, such as glucose, in the absence of oxygen.

Question 10

What is a respiratory substrate?

Answer 10

An organic substrate that can be used for respiration.

Question 11

Give examples if why we need to respire.

Answer 11

Active transport.
Endocytosis.
Replication of DNA/interphase.
Secretion.
Movement.
Cell replication, meiosis.

Question 12

Describe the structure of ATP.

Answer 12

Adenine.
Ribose sugar.
3 phosphate.

Can be hydrolysed to ADP and an inorganic phosphate.

Question 13

What is the role of NAD?

Answer 13

Coenzyme.

Carries hydrogen atom which can later be split to H+ and e-

Question 14

What are the products of glycolysis?

Answer 14

2 x ATP (4 made but 2 used)
2 x red NAD
2 x pyruvate

Question 15

Describe the stages of glycolysis.

Answer 15

One ATP molecule is hydrolysed and the phosphate group attaches the glucose molecule at carbon 6.

Glucose-6-phosphate is changed to fructose-6-phosphate.

Another ATP is hydrolysed and attaches to fructose at C1. Now fructose 1,6-bisphosphate.
Becomes Hexose 1,6-bisphosphate.

Each molecule of H1,6B us split into two molecule of triose phosphate.

Using dehydrogenase enzymes two hydrogen atoms are removed from each triose phosphate molecule.

NAD combines with the H atoms to form red NAD.

2 molecules of ATP are formed - substrate level phosphorylation.

Enzyme catalysed reactions convert each triose phosphate molecule to pyruvate.
2 molecules of ADP are also phosphorylated by substrate level p.

Question 16

Describe the ultrastructure of mitochondria.

Answer 16

An intermembrane space between the inner and outer phospholipid membrane.

Outer membrane is smooth
Inner membrane is folded into cristae to give a larger surface area.

The matrix is enclosed by the inner membrane, contains proteins, lipids, enzymes etc.

Question 17

How does mitochondria structure help them carry out their function?

Answer 17

Matrix:
Enzymes to catalyse reactions.
Contains coenzyme NAD. Ribosomes where proteins are assembled.
Mitochondrial DNA to code for enzymes and proteins.

Outer membrane:
Channel/carrier proteins to allow pyruvate to pass.

Inner membrane:
Impermeable I most small ions, eg H+.
Folded cristae gives large surface area.
Electron carriers and ATP synthase enzymes embedded in it.

Question 18

Describe electron carriers.

Answer 18

Protein complexes arranged in electron transport chains.

Each electron carrier is an enzyme, with haem cofactors, containing iron

Cofactor can accept and donate electrons as iron Fe2+ oxidised/reduced and donating to the next carrier.

Oxidoreductase enzymes in reduction and oxidation reactions.

Some carriers have a coenzyme that pump protons from the matrix to the intermembrane space.

Because the inner membrane is impermeable to small ions protons accumulate in the IM space, a source of energy.

Question 19

Describe the ATP synthase enzymes.

Answer 19

Large and protrude from the inner membrane into the matrix.

Allow protons to pass through them down a concentration gradient (chemiosmosis).

The proton motive force drives the rotation if part of the enzyme and joins ADP to pi.

Question 20

Describe the link reaction.

Answer 20

Pyruvate dehydrogenase and decarboxylase remove H and a carboxyl group from pyruvate.

This produces CO2.
Coenzyme NAD accepts the H.
Coenzyme A accepts acetate to become acetyl coenzyme A.

Question 21

How is ATP indirectly made from the link reaction?

Answer 21

Red NAD carries2 H atoms to be used in oxidative phosphorylation.

Question 22

Describe the Krebs cycle.

Answer 22

Acetate is offloaded by coenzyme A and joins oxaloacetate to form citrate.

Citrate is deC and deH to form a 5C compound.
This produces CO2 and a molecule of NAD accepts 2 H to become red.

5C is deC and deH to form a 4C compound.
CO2 and red NAD.

4C changed to another 4C.
SLP makes ADP phosphorylated to ATP.

4C changed to 4C, pair of H removed and accepted by coenzyme FAD to become red.

4C deC and deH to regenerate oxaloacetate.
Another NAD is red.

Question 23

What is the frequency of the Krebs cycle?

Answer 23

One turn for each molecule of acetate, since link produces 2 acetate per 1 pyruvate.

2 turns per glucose.

Question 24

What are the products of the link reaction?

Answer 24

2 red NAD

2 CO2

Question 25

What are the products of the Krebs cycle?

Answer 25

6 red NAD.
2 red FAD.
4 CO2.
2 ATP.

Question 26

Where does oxidative phosphorylation occur?

Answer 26

Inner mitochondrial membrane.

Question 27

Describe how oxidative phosphorylation occurs?

Answer 27

Chemiosmosis occurs.

The electrons are passed from the last electron carrier to oxygen, which is the final electron acceptor.

H+ also join so oxygen is reduced to water.

Question 28

Why is the potential number of ATP molecules in oxidative phosphorylation rarely met?

Answer 28

Protons leaking across the mitochondrial membrane reduced the proton motive force.

Some ATP actively transports pyruvate into the mitochondria.

Question 29

Describe how animals respire anaerobically?

Answer 29

Lactate fermentation.
When the ATP demand is high and there is an oxygen deficit.

Red NAD is oxidised to NAD.
Pyruvate is a hydrogen acceptor.
It accepts H from red NAD.

Lactate dehydrogenase catalyses oxidation of red NAD and reduction of pyruvate to lactate.

Can be recycled to glucose/glycogen.
Can be carried to the liver and converted back to pyruvate if oxygen is present.

Question 30

Describe how fungi respire anaerobically.

Answer 30

Alcoholic fermentation.

Each pyruvate molecule loses a CO2 molecule, catalysed by pyruvate decarboxylase.
Turns it to ethanal.

Ethanal accepts H atoms from red NAD to turn to ethanol, catalysed by ethanol dehydrogenase.

Question 31

How much energy do carbohydrates, lipids and proteins comparatively release?

Answer 31

Carbohydrate< lipid by a lot